A Doherty Architecture With High Feasibility and Defined Bandwidth Behavior

This paper presents a complete and rigorous theoretical investigation of a Doherty architecture with a novel output combining network. The benefits in terms of bandwidth and feasibility held by the proposed topology are investigated and compared with the conventional one. In particular, the theoretical analysis demonstrates that the proposed output combiner allows to implement a Doherty amplifier with defined bandwidth (narrower or broader) without worsening in performances. Moreover, the proposed solution results in a more feasible structure with respect to the classical one, especially when high output power levels are sought. The theoretical results are validated through the design and realization of a prototype based on commercial GaN active devices. Experimental results show 42-dBm output power and 65% peak efficiency with a flat behavior in the 1.95-2.25-GHz frequency band (i.e., 14% of relative bandwidth) under continuous wave signal. Moreover, 50% average efficiency at 38-dBm average output power with -45 dBc of adjacent channel power ratio is demonstrated under 5-MHz 3GPP driving signal using a simple polynomial digital pre-distortion.